Evaluating the patient with loss of consciousness.

INTRODUCTION

Patients who have had an episode of altered awareness and are subsequently brought to the hospital for evaluation are common[9] amounting to more than 6% of all emergency room (ER) admissions. One of the key elements in properly evaluating these patients is to perform a good history. The history can come from a number of different sources including the patient, family, and/or others present at the time of the event. In each case, the information provided may be biased by the preconceptions of the person providing the history. Thus, it is critical to understand which aspects of the history are most important and most reliable in distinguishing between the possible diagnoses. For example, it is not uncommon for an observer to state that a patient was unconscious if he/she did not respond to voice. Only further questioning about other characteristics of the patient at that time such as loss of tone or abnormal movements may help sort out the actual events.

It is also common for providers to lump all patients with transient alterations of awareness under the diagnosis of syncope. It is thus essential to clearly define the term syncope. The Merriam-Webster Dictionary defines syncope as “loss of consciousness (LOC) resulting from insufficient blood flow to the brain.”[5] There are various conditions that can be mistaken for syncope and it is important that a correct diagnosis be made because management and care will differ depending on that diagnosis. In this paper we will primarily address the issue of distinguishing a neurological cause versus a cardiac cause for a transient alteration of awareness; but it is important as well to cover the factors that place a patient at high risk for a serious cardiac event.

The differential diagnoses

In order to obtain an optimal history, it is important to be aware of the diagnoses that could potentially cause the patient's symptoms. Soteriades[9] reviewed data from the Framingham study for all patients with a diagnosis of syncope and was able to determine the eventual cause for syncope. [Table 1] shows the incidence of various etiologies in patients with and without cardiac disease. It is clear that neurologic causes are not common compared with cardiac and vaso-vagal causes of syncope; but they nonetheless form an important subset of all patients with an initial diagnosis of syncope. [Table 2] provides a larger list of some conditions that could be associated with an apparent LOC. It is important to realize that the initial determination of LOC is generally made by a lay person without a medical background; and so the differential diagnosis must be extended to include diagnoses that medical personnel would not always associate with unconsciousness.

Table 1

Causes of syncope from Soteriades[9] in patients with and without cardiovascular disease

Table 2

Conditions that could present with loss of consciousness concentrating on neurological causes

[Table 3] shows some of the typical symptoms for “LOC.” Witnesses will likely describe an event in their own terms but will often not attend to the preceding or subsequent events that are critical to making the diagnosis. Therefore, follow up questions are very important to create a timeline describing the event in detail. [Table 4] shows some frequently obtained elements of the history in patients with syncope, stroke, transient ischemic attack (TIA), delirium, and seizures. Hoefnagels[4] studied some of the factors in the history that helped determine whether a patient had syncope or seizure. These factors are abstracted in Table 5a and 5b; and show the importance of observing whether the patient had pallor/sweating before the event as a predictor for syncope. The observation that the patient was “blue” was strongly predictive of seizure as was disorientation and tongue biting.

Table 3

Symptoms for loss of consciousness used by non-medical providers. All of these need to be interpreted

Table 4

Historical elements in patients describing the time around the event of altered consciousness and their prevalence in various diseases

Table 5a

Individual symptoms and the risk of seizure versus nonseizure according to Hoefnagels[4]

Table 5b

The probability of seizure as a function of various combinations of four symptoms according to Hoefnagels[4]

Besides the questions shown in Tables 4 and 5, there are other important questions whose answers may be useful in making the diagnosis of vaso-vagal syncope versus other cardiac conditions. These have been addressed by prior studies that try to use elements of the history and physical examination to predict patients presenting with apparent syncope that are at high risk of serious adverse events. One such study led to the creation of the Calgary syncope symptom score.[8] This scale involves asking the seven questions detailed in Table 6 and has been demonstrated to have an overall sensitivity of 87% and specificity of 32% in making the diagnosis of vasovagal syncope. Another set of questions comes from the analyses that led to the Boston syncope rule.[23] These investigators asked questions in eight categories and considered the patient at high risk for an adverse outcome (and hence unlikely to be vaso-vagal syncope) if the patient had symptoms or signs in any of the following categories: (i) Signs or symptoms of acute coronary syndrome, (ii) signs of cardiac conduction diseases, (iii) worrisome cardiac history, (iv) valvular heart disease by history or examination, (v) family history of sudden death, (vi) persistent abnormal vital signs, (vii) volume depletion, or (viii) primary central nervous system (CNS) event. This rule was 97% sensitive and 62% specific in finding patients with an adverse outcome of an apparent syncopal event. The San Francisco syncope rule[67] uses the mnemonic CHESS to identify patients at high risk for adverse outcomes. C stands for a history of congestive heart failure, H-Hematocrit <30%, E-abnormal ECG, S-shortness of breath, S-triage systolic blood pressure <90 mmHg. Other scores such as the ROSE score and the OESIL score include bradycardia, chest pain, oxygen saturation <94%, age >65, and syncope without a prodrome as risk factors.[1] Age is a very important predictor as the incidence of syncope is at least 4 times higher in those older than 80 as opposed to those aged less than 50 years.[9]

Table 6

The calgary syncope score.[8] The total score is the sum of the scores for all positive answers. Vasovagal syncope is diagnosed if the total point score is >=–2. The annotation (none) regarding question 4 indicated that none of the patients remembered being unconscious

Physical examination

The physical examination can reveal more about the reasons for a patient's LOC. Overall, the examination is targeted toward finding signs of cardiac disease and any evidence of neurologic illness. Useful physical findings in patients presenting with loss of consciousness. [Table 7] lists the various findings on examination and their interpretation.[8]

Table 7

Useful physical findings in patients presenting with loss of consciousness

Summary

Although there has been much literature dedicated to making the correct diagnosis in a patient who presents with a transientl altered level of consciousness, the concept remains difficult and is strongly dependent upon the provider's skill in obtaining a complete history and physical examination.